Haw. Rev. Stat. § 476-17: Subsequent inclusion of other security.

In a contract for a sale primarily for a personal, family, or household purpose, no provision for the subsequent inclusion of title to or a subsequent lien upon or a subsequent security interest in any goods, other than the goods which are the subject matter of or original security for the credit sale, or accessories thereto, or special or auxiliary equipment used in connection therewith, or in substitution, in whole or in part, for any thereof, as security for payment of the time sale price, shall be enforceable.